Nuclear Theory·nucl-th

Monday·September 14, 2020

8 papers—6 primary·2 cross-listed

07
[Submitted on 11 Sept 2020] (cross-list from nucl-ex)
Isotopic equilibrium constants for very low-density and low-temperature nuclear matter
J. B. Natowitz · H. Pais · G. Roepke · J. Gauthier · K. Hagel · M. Barbui · R. Wada
Yields of equatorially emitted light isotopes, $1 \leq Z \leq 14$ , observed in ternary fission in the reaction $^{241}$ Pu( $n_{th}$ ,f) are employed to determine apparent chemical equilibrium constants for low-temperature and low-density nuclear matter. The degree of liberation and role of medium modifications are probed through a comparison of experimentally derived reaction quotients with equilibrium constants calculated using a relativistic mean-field model employing a universal medium modification correction for the attractive $σ$ meson coupling. The results of these comparisons indicate that equilibrium is achieved for the lighter ternary fission isotopes. For the heavier isotopes experimental reaction quotients are well below calculated equilibrium constants. This is attributed to a dynamical limitation reflecting insufficient time for full equilibrium to develop. The role of medium effects leading to yield reductions is discussed as is the apparent enhancement of yields for $^{8}$ He and other very neutron rich exotic nuclei.
Comments:
8 pages, 2 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.05200 [pdf]
PRC(2020)·5 citations
08
[Submitted on 11 Sept 2020] (cross-list from hep-lat)
Lattice QCD constraints on the parton distribution functions of $^{3} He$
William Detmold🇺🇸 · Marc Illa🇪🇸 · David J. Murphy🇺🇸 · Patrick Oare🇺🇸 · Kostas Orginos🇺🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸 · Frank Winter🇺🇸
The fraction of the longitudinal momentum of $^{3} He$ that is carried by the isovector combination of $u$ and $d$ quarks is determined using lattice QCD for the first time. The ratio of this combination to that in the constituent nucleons is found to be consistent with unity at the few-percent level from calculations with quark masses corresponding to $m_{π} \sim 800$ MeV, extrapolated to the physical quark masses. This constraint is consistent with, and significantly more precise than, determinations from global nuclear parton distribution function fits. Including the lattice QCD determination of the momentum fraction in the nNNPDF global fitting framework results in the uncertainty on the isovector momentum fraction ratio being reduced by a factor of 2.5, and thereby enables a more precise extraction of the $u$ and $d$ parton distributions in $^{3} He$ .
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.05522 [pdf]
PRL(2021)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE

Isotopic equilibrium constants for very low-density and low-temperature nuclear matter

Lattice QCD constraints on the parton distribution functions of 3He

Affiliations

Lattice QCD constraints on the parton distribution functions of $^{3} He$